Semiconductor device and method of manufacturing the same

ABSTRACT

A method includes burying a conductive pattern in an insulating film made of SiOH, SiCOH or organic polymer, treating surfaces of the insulating film and the conductive pattern with plasma which includes a hydrocarbon gas as a treatment gas, and forming a diffusion barrier film, which is formed of an SiCH film, an SiCHN film, an SiCHO film or an SiCHON film, over the insulating film and the conductive pattern with performing a plasma CVD by adding an Si-containing gas to the treatment gas while increasing an addition amount gradually or in a step by step manner.

This application is based on Japanese patent application NO.2008-290977, the content of which is incorporated hereinto by reference.

BACKGROUND

1. Technical Field

The present invention relates to a semiconductor device including adiffusion barrier film formed over an insulating film and a conductivepattern, and a method of manufacturing the same.

2. Related Art

In recent years, copper has been used as interconnect material forsemiconductor devices. Copper interconnect is formed in the form ofbeing buried in an insulating film. When copper is used as interconnectmaterial for semiconductor devices, a diffusion barrier film is requiredto be formed over the copper interconnect in order to prevent the copperfrom being diffused to an upper layer of the copper interconnect. Whenthe diffusion barrier film is formed over the copper interconnect, it isnecessary to secure adhesion between the copper interconnect and thediffusion barrier film and adhesion between the insulating film in whichthe copper interconnect is buried and the diffusion barrier film.

Japanese Laid-open patent publication NO. 2002-203899 discloses atechnique for exposing a copper layer to reducing plasma andcarbon-containing plasma before forming an inorganic barrier film overthe copper layer in order to improve adhesion between the inorganicbarrier film and the copper layer.

With miniaturization of semiconductor devices, there is a need to reduceinter-interconnect capacitance. Lowering of a relative permittivity ofan insulating film in which an interconnect is buried is effective inreducing the inter-interconnect capacitance. An example of theinsulating film having a low relative permittivity may include an SiOHfilm, an SiCOH film or an organic polymer film.

The present inventor has recognized as follows. A process of burying aconductive pattern such as a copper pattern or the like in theinsulating film includes a chemical mechanical polishing (CMP) process.In the CMP process, since the conductive pattern is physically polishedwhile being oxidized, an oxide layer is left on a surface layer of theconductive pattern after the CMP process. This residual oxide layerdeteriorates an electro-migration characteristic of the conductivepattern. In addition, when an SiOH film, an SiCOH film or an organicpolymer film is used as the insulating film, a surface layer of theinsulating film is oxidized in the CMP process and its relativepermittivity is raised.

It may be contemplated that a surface layer of the copper pattern isexposed to a reducing atmosphere as a method of eliminating the oxidelayer on the surface layer of the conductive pattern. However, thepresent inventor has studied this method and has found that this methodexposes a surface layer of the insulating film to the reducingatmosphere, thereby further raising the relative permittivity of thesurface layer of the insulating film.

Another finding of the studies of the present inventor is that, when therelative permittivity of the surface layer of the insulating film israised, it was revealed that the relative permittivity of the surfacelayer of the insulating film is lowered if the surface layer of theinsulating film is treated by plasma of carbon-containing gas. However,it was also revealed that adhesion between the insulating film and adiffusion barrier film is lowered if the surface layer of the insulatingfilm is treated by carbon-containing plasma.

In this manner, when the SiOH, SiCOH or organic polymer is used as theinsulating film, it is difficult to prevent the oxide layer from beingleft on the surface layer of the conductive pattern, prevent therelative permittivity of the surface layer of the insulating film frombeing raised, and prevent the adhesion between the insulating film andthe diffusion barrier film from being lowered.

SUMMARY

In one embodiment, there is provided a method of manufacturing asemiconductor device, including: burying a conductive pattern in aninsulating film made of SiOH, SiCOH or organic polymer; treatingsurfaces of the insulating film and the conductive pattern with plasmawhich includes a hydrocarbon gas as a treatment gas; and forming adiffusion barrier film, which is formed of an SiCH film, an SiCHN film,an SiCHO film or an SiCHON film, over the insulating film and theconductive pattern with performing a plasma CVD by adding anSi-containing gas to the treatment gas while increasing the additionamount gradually or in a step by step manner.

According to the method of manufacturing a semiconductor device, in thesurface treating step, activated hydrogen can be supplied to the surfacelayer of the conductive pattern. Accordingly, even when an oxide layeris formed on the surface layer of the conductive pattern in the buryingstep, the oxide layer can be reduced in the surface treating step. Inaddition, in the surface treating step, a deterioration layer formed onthe surface layer of the insulating film can be modified by activatedcarbon. Accordingly, even when a relative permittivity of the surfacelayer of the insulating film is raised in the burying step, the relativepermittivity of the surface layer of the insulating film can be lowered.In addition, in the surface treating step, a CH film or a CHN film maybe formed over the insulating film and the conductive pattern.

In the meantime, in the film forming step, the Si-containing gas isadded to the treatment gas including the hydrocarbon gas whileincreasing the addition amount gradually or in a step by step manner.Accordingly, the diffusion barrier film has an Si concentration whichincreases gradually or in a step by step manner in an upward direction.Accordingly, even when the CH film or the CHN film is formed over theinsulating film and the conductive pattern in the surface treating step,it is possible to prevent adhesion between the CH film or the CHN filmand the diffusion barrier film from being lowered.

In this manner, according to the present invention, even when the SiOH,SiCOH or organic polymer is used as the insulating film, it is possibleto prevent an oxide layer from being left on the surface layer of theconductive pattern, prevent the relative permittivity of the surfacelayer of the insulating film from being raised, and prevent adhesionbetween the insulating film and the diffusion barrier film from beinglowered.

In another embodiment, there is provided a semiconductor deviceincluding: an insulating film made of SiOH, SiCOH or organic polymer; aconductive pattern buried in the insulating film; and a diffusionbarrier film which is located over the insulating film and theconductive pattern and is formed of an SiCH film, an SiCHN film, anSiCHO film or an SiCHON film. The diffusion barrier film includes an Siconcentration which increases in an upward direction gradually or in astep by step manner.

According to the present invention, even when the SiOH, SiCOH or organicpolymer is used as the insulating film, it is possible to prevent anoxide layer from being left on the surface layer of the conductivepattern, prevent the relative permittivity of the surface layer of theinsulating film from being raised, and prevent adhesion between theinsulating film and the diffusion barrier film from being lowered.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the presentinvention will be more apparent from the following description ofcertain preferred embodiments taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1A and 1B are sectional views showing a method of manufacturing asemiconductor device according to a first embodiment;

FIGS. 2A and 2B are sectional views showing a method of manufacturing asemiconductor device according to the first embodiment;

FIG. 3 is a graph schematically showing a dependency of an Siconcentration in a film thickness direction in a laminated film (orcontinuous film) including a CH film and a diffusion barrier film;

FIG. 4 is a sectional view showing a method of manufacturing asemiconductor device according to a second embodiment; and

FIG. 5 is a sectional view showing a configuration of a semiconductordevice according to a third embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention will be now described herein with reference toillustrative embodiments. Those skilled in the art will recognize thatmany alternative embodiments can be accomplished using the teachings ofthe present invention and that the invention is not limited to theembodiments illustrated for explanatory purposes.

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to the accompanying drawings. Throughout thedrawings, like elements are denoted by like reference numerals andexplanation thereof will not be repeated.

FIGS. 1A, 1B, 2A and 2B are sectional views showing a method ofmanufacturing a semiconductor device according to a first embodiment.This method of manufacturing a semiconductor device includes a buryingprocess, a first surface treating process and a film forming process.The burying process is a process of burying a conductive pattern 200 inan insulating film 100 made of SiOH, SiCOH or organic polymer. The firstsurface treating process is a process of treating surfaces of theinsulating film 100 and the conductive pattern 200 with plasma with atreatment gas which includes a hydrocarbon gas. The film forming processis a process of forming a diffusion barrier film 302 formed of an SiCHfilm, SiCHN film, SiCHO film or SiCHON film over the insulating film 100and the conductive pattern 200 using a plasma CVD by adding anSi-containing gas to the treatment gas while increasing the additionamount gradually or in a step by step manner. Hereinafter, theseprocesses will be described in detail.

As shown in FIG. 1A, first, the insulating film 100 made of SiOH, SiCOHor organic polymer is formed. The insulating film 100 may be a porousfilm having a plurality of holes (whose diameter is for example equal toor less than 10 nm). A relative permittivity of the insulating film isequal to or less than 2.7. “Silk” (trade mark, available from The DowChemical Co.) may be used as the organic polymer of which the insulatingfilm 100 is formed.

Next, a silicon oxide film (not shown) is formed over the insulatingfilm 100, and then the silicon oxide film and the insulating film 100are selectively etched. Thus, a groove is formed in the insulating film100.

Next, a diffusion barrier film 204 is formed in the groove and over thesilicon oxide film on the insulating film 100 using, for example, asputtering process. The diffusion barrier film 204 is for example atantalum film. Next, a conductive film is formed over the diffusionbarrier film 204 by, for example, carrying out formation of a seed film(for example, a Cu seed film) by a sputtering process and electroplatingin this order, and additionally, the conductive film, the diffusionbarrier film 204 and the silicon oxide film located over the insulatingfilm 100 are removed by a CMP process. Thus, the diffusion barrier film204 and the conductive pattern 200 are buried in the insulating film100. The conductive pattern 200 is, for example, copper interconnect.When the conductive pattern 200 is copper interconnect, adjacent copperinterconnects are for example equal to or less than 75 nm in theirmutual intervals and equal to or less than 150 nm in a distance betweentheir centers.

In the CMP process, an oxide layer 202 (for example a CuO layer) isformed on a surface layer of the conductive pattern 200. In addition,since a surface layer of the insulating film 100 is polished by the CMPprocess, a deterioration layer 102 with a high relative permittivity isalso formed on the surface layer of the insulating film 100. If theinsulating film 100 is an SiCOH film, the deterioration layer 102 is forexample formed when a methyl group of the surface layer of the SiCOHfilm is destroyed to generate an Si—OH bond or a dangling bond of Si. Ifthe insulating film 100 is an SiOH layer, the deterioration layer 102 isfor example formed when a dangling bond of Si is generated. If theinsulating film 100 is an organic polymer layer, the deterioration layer102 is nearly sublimated, with a dangling bond of C left on a surfacelayer of the organic polymer layer.

Next, as shown in FIG. 1B, the surface of the insulating film 100 andthe surface of the conductive pattern 200 are treated by plasma with atreatment gas which includes a hydrocarbon gas. The hydrocarbon gas isfor example ethene (ethylene) but may be any of other hydrocarbon gases(for example CH4, C2H4 or the like). In addition, the treatment gas maybe a 100% hydrocarbon gas or may contain He of equal to or more than 50Vol % and equal to or less than 99 Vol %, which is a carrier gas, inaddition to the hydrocarbon gas.

The plasma contains activated hydrogen (hydrogen ions, hydrogen radicalsor the like) and activated carbon (carbon ions, carbon radicals or thelike). Accordingly, since the oxide layer 202 formed on the surfacelayer of the conductive pattern 200 is reduced by the activated hydrogenand carbon is introduced in the oxide layer 202, the oxide layer 202becomes a carbon-containing Cu layer 206. In addition, the Si—OH bond orthe Si dangling bond of the deterioration layer 102 formed on thesurface layer of the insulating film 100 is turned to an Si—CH bond bythe activated carbon and hydrogen, thereby modifying the deteriorationlayer 102.

In addition, in this process, a CH film 300 may be formed on the surfaceof the insulating film 100 and the surface of the conductive pattern200. The thickness of the CH film 300 is for example equal to or morethan 1 nm and equal to or less than 10 nm. In the CH film 300, C is forexample equal to or less than 25% by the number of atoms with respect toH. In addition, C is introduced in the surface layer of the conductivepattern 200.

Next, as shown in FIG. 2A, a plasma CVD is performed by adding anSi-containing gas to the treatment gas while increasing the additionamount gradually or in a step by step manner. An example of theSi-containing gas may include a trimethylsilane gas or other gases (forexample tetramethylsilane, dimethylsilane, monomethylsilane,tetravinylsilane, trivinylmonomethylsilane, trimethylsilane,divinylsilane, divinyldimethylsilane, monovinyltrimethylsilane,monovinylsilane, monosilane, trimethylphenylsilane,dimethyldiphenylsilane, phenylsilane, diphenoldisilane, or the like.).In addition, when the Si-containing gas is added, the plasma may bedropped once or may remain unchanged. Accordingly, a diffusion barrierfilm 302, which is an SiCH film, an SiCHN film, an SiCHO film or anSiCHON film, is formed over the CH film 300. When the addition of theSi-containing gas is started maintaining the plasma, the diffusionbarrier film 302 is formed to be continued to the CH film 300. Thethickness of the diffusion barrier film 302 is for example equal to ormore than 5 nm and equal to or less than 50 nm. The Si concentration ofthe diffusion barrier film 302 increases in an upward directiongradually or in a step by step manner. The Si concentration in thediffusion barrier film 302 is for example equal to or more than 5 atomic% and equal to or less than 30 atomic % on average.

Next, as shown in FIG. 2B, an insulating film 104 is formed over thediffusion barrier film 302. The insulating film 104 is for example aninterlayer insulating film and is for example made of SiOH, SiCOH ororganic polymer. The insulating film 104 may be a porous film and mayhave a relative permittivity of equal to or less than 2.7.

The semiconductor device formed in this manner has the insulating film100, the conductive pattern 200 and the diffusion barrier film 302. Theconductive pattern 200 is buried in the insulating film 100 and thediffusion barrier film 302 is located over the insulating film 100 andthe conductive pattern 200. The diffusion barrier film 302 has the Siconcentration which increases in the upward direction gradually or in astep by step manner. In addition, the CH film 300 is interposed betweenthe insulating film 100 and the conductive pattern 200, and thediffusion barrier film 302.

FIG. 3 is a graph schematically showing a dependency of the Siconcentration in a film thickness direction in a laminated film (orcontinuous film) including the CH film 300 and the diffusion barrierfilm 302. No Si is contained in the CH film 300. Almost no Si iscontained in the diffusion barrier film 302 at an interface with the CHfilm 300. The diffusion barrier film 302 has the Si concentration whichincreases gradually or in a step by step manner as it becomes distantfrom the interface with the CH film 300 (that is, in a positive filmthickness direction).

Next, the operation and effect of this embodiment will be described.This embodiment has the process of treating the surfaces of theinsulating film 100 and conductive pattern 200 with the plasma with thetreatment gas including the hydrocarbon gas. Accordingly, the oxidelayer 202 formed on the surface layer of the conductive pattern 200 isreduced by the activated hydrogen.

The Si—OH bond or the Si dangling bond of the deterioration layer 102formed on the surface layer of the insulating film 100 is turned to theSi—CH bond by the activated carbon and hydrogen. Accordingly, thedeterioration layer 102 is modified. Accordingly, it is possible toprevent the relative permittivity of the surface layer of the insulatingfilm 100 from being raised. In addition, when a plurality of conductivepatterns 200 is formed in the insulating film 100, it is possible toprevent a time dependent dielectric breakdown (TDDB) characteristicbetween these conductive patterns 200 from being deteriorated.

In addition, in the process of forming the diffusion barrier film 302,the Si-containing gas is added to the treatment gas including thehydrocarbon gas while increasing the addition amount gradually or in astep by step manner. As a result, the diffusion barrier film 302 has theSi concentration which increases in the upward direction gradually or ina step by step manner. Accordingly, even when the CH film 300 is formedon the surfaces of the insulating film 100 and conductive pattern 200,it is possible to prevent the adhesion between the insulating film 100and the diffusion barrier film 302 from being lowered.

In this manner, according to this embodiment, when the insulating film100 is made of the SiOH, SiCOH or organic polymer, it is possible toprevent an oxide layer from being left on the surface layer of theconductive pattern 200, prevent the relative permittivity of the surfacelayer of the insulating film 100 from being raised, and prevent theadhesion between the insulating film 100 and the diffusion barrier film302 from being lowered. Accordingly, the reliability of thesemiconductor device is improved. This effect is particularly noticeablewhen the diffusion barrier film 302 is formed to be continued to the CHfilm 300.

If the adhesion between the insulating film 100 and the diffusionbarrier film 302 is lowered, water may penetrate into through a gapbetween the insulating film 100 and the diffusion barrier film 302. Ifthe insulating film 100 is a porous film, the insulating film 100absorbs the water, thereby decreasing a breakdown voltage of theinsulating film 100 and increasing an inter-interconnect capacitance inthe same layer as the insulating film 100. As described above, accordingto this embodiment, since the adhesion between the insulating film 100and the diffusion barrier film 302 can be prevented from being lowered,it is possible to prevent such a problem from occurring.

In addition, since C is introduced in the surface layer of theconductive pattern 200, even when oxygen is diffused into the surface ofthe conductive pattern 200, the oxygen preferentially reacts with thecarbon, thereby preventing an oxide layer from being formed on thesurface layer of the conductive pattern 200. Accordingly, anelectro-migration of the conductive pattern 200 is improved.

FIG. 4 is a sectional view showing a method of manufacturing asemiconductor device according to a second embodiment. The method ofmanufacturing a semiconductor device according to this embodiment hasthe same processes as those of the first embodiment except that theformer includes a second surface treating process between the buryingprocess of burying the conductive pattern 200 in the insulating film 100and the first surface treating process of treating the surfaces of theinsulating film 100 and conductive pattern 200 with the plasma with thetreatment gas including the hydrocarbon gas. The second surface treatingprocess is a process of treating the surfaces of the insulating film 100and conductive pattern 200 with a reducing plasma. The reducing plasmais a plasma with a treatment gas including, for example, ammonia but maybe a plasma with a treatment gas which includes hydrogen.

This embodiment can obtain the same effects as the first embodiment. Inaddition, in the second surface treating process, the oxide layer 202formed on the surface layer of the conductive pattern 200 can be reducedin a short time. In addition, in the second surface treating process,even when the relative permittivity of the deterioration layer 102 onthe surface layer of the insulating film 100 is further raised, it ispossible to prevent the relative permittivity of the surface layer ofthe insulating film 100 from being raised by modifying the deteriorationlayer 102 in the first surface treating process.

FIG. 5 is a sectional view showing a configuration of a semiconductordevice according to a third embodiment. This semiconductor device has astructure in which an interlayer insulating film 30 and an insulatinglayer 110 are formed over a substrate 10 on which a transistor 20 isformed and additional insulating layers 120, 130, 140 and 150 arestacked in that order.

The insulating layer 110 is for example a silicon oxide film and mayhave the same configuration as the insulating film 100 in the first orsecond embodiment. A conductive pattern 210 is buried in the insulatinglayer 110. The conductive pattern 210 has the same configuration as theconductive pattern 200 in the first or second embodiment. The conductivepattern 210 is connected to the transistor 20 through, for example, acontact buried in the interlayer insulating film 30.

The insulating layers 120, 130 and 140 have the same configuration asthe insulating film 100 in the first or second embodiment and arerespectively buried therein with conductive patterns 220, 230 and 240.The conductive patterns 220, 230 and 240 have the same configuration asthe conductive pattern 200 in the first or second embodiment and areformed in the same manner as the conductive pattern 200. In addition, adiffusion barrier film (not shown) having the same configuration as thediffusion barrier film 204 in the first embodiment is provided betweenthe conductive patterns 220, 230 and 240 and the insulating layers 120,130 and 140.

In addition, a CH film 310 and a diffusion barrier film 312 are stackedin this order between the insulating layer 110 and the insulating layer120. Similarly, a CH film 320 and a diffusion barrier film 322, a CHfilm 330 and a diffusion barrier film 332, and a CH film 340 and adiffusion barrier film 342 are respectively stacked between theinsulating layer 120 and the insulating layer 130, between theinsulating layer 130 and the insulating layer 140, and between theinsulating layer 140 and the insulating layer 150. These stacked layershave the same configuration as the stacked layers including the CH film300 and the diffusion barrier film 302 in the first embodiment and areformed in the same manner as the stacked layers including the CH film300 and the diffusion barrier film 302.

This embodiment can also obtain the same effects as the first or secondembodiment.

Although the various embodiments of the present invention have beenshown and described above with reference to the drawings, theseembodiments are only examples of the present invention which may employvarious other configurations. For example, although the CH film 300 isformed between the insulating film 100 and the conductive pattern 200,and the diffusion barrier film 302 in each of the above embodiments, theCH film 300 does not need to be formed.

In addition, in the process shown in FIG. 1B, a nitrogen-containing gas(for example NH3, N2 or the like) may be added to the treatment gas. Inthis case, instead of the CH film 300, a CHN film is formed on thesurface of the insulating film 100 and the surface of the conductivepattern 200. In this case, the same effects as above can also beobtained. In addition, since a breakdown voltage of the CHN film ishigher than that of the CH film 300, the breakdown voltage between upperand lower interconnects is raised.

It is apparent that the present invention is not limited to the aboveembodiments, but may be modified and changed without departing from thescope and spirit of the invention.

1. A method of manufacturing a semiconductor device, comprising: buryinga conductive pattern in an insulating film made of SiOH, SiCOH ororganic polymer; treating surfaces of said insulating film and saidconductive pattern with plasma which includes a hydrocarbon gas as atreatment gas; and forming a diffusion barrier film, which is formed ofan SiCH film, an SiCHN film, an SiCHO film or an SiCHON film, over saidinsulating film and said conductive pattern with performing a plasma CVDby adding an Si-containing gas to said treatment gas while increasingthe addition amount gradually or in a step by step manner.
 2. The methodas set forth in claim 1, wherein said insulating film is a porous filmincluding a plurality of holes.
 3. The method as set forth in claim 1,wherein a relative permittivity of said insulating film is equal to orless than 2.7.
 4. The method as set forth in claim 1, wherein said stepof treating surfaces of said insulating film and said conductive patternincludes forming a CH film or a CHN film on said surfaces of saidinsulating film and said conductive pattern.
 5. The method as set forthin claim 4, wherein said step of forming a diffusion barrier filmincludes forming said diffusion barrier film to be continued to said CHfilm or said CHN film.
 6. The method as set forth in claim 5, whereinsaid step of forming diffusion barrier film is performed by starting theaddition of said Si-containing gas while said plasma being maintained insaid step of treating surfaces of said insulating film and saidconductive pattern.
 7. The method as set forth in claim 1, wherein saiddiffusion barrier film includes an Si concentration which increases inan upward direction gradually or in a step by step manner.
 8. The methodas set forth in claim 1, further comprising between said step of buryinga conductive pattern in an insulating film and said step of treatingsurfaces of said insulating film and said conductive pattern: retreatingsaid surfaces of said insulating film and said conductive pattern with areducing plasma.
 9. A semiconductor device comprising: an insulatingfilm made of SiOH, SiCOH or organic polymer; a conductive pattern buriedin said insulating film; and a diffusion barrier film which is locatedover said insulating film and said conductive pattern and is formed ofan SiCH film, an SiCHN film, an SiCHO film or an SiCHON film, whereinsaid diffusion barrier film includes an Si concentration which increasesin an upward direction gradually or in a step by step manner.
 10. Thesemiconductor device as set forth in claim 9, wherein a CH film or a CHNfilm is provided between said insulating film and said conductivepattern, and said diffusion barrier film.
 11. The semiconductor deviceas set forth in claim 9, wherein said insulating film is a porous filmincluding a plurality of holes.
 12. The semiconductor device as setforth in claim 9, wherein a relative permittivity of said insulatingfilm is equal to or less than 2.7.
 13. The semiconductor device as setforth in claim 9, wherein a surface layer of said conductive patterncontains C.